In a method of immunoassaying a component to be measured in blood that exists outside blood cells such as red and white blood cells, serum or plasma prepared by removing blood cells from whole blood is used as a sample. However, since removal of blood cells requires special equipments such as a centrifuge and is troublesome, methods of measurement using whole blood as a sample have been proposed (see Patent Document 1). When whole blood is used as a sample, it is problematic that a measurement is affected by blood cell components such as hemoglobin or blood cell membrane components contaminated in the sample through hemolysis. These components affect the optical detection system, inhibit immunoreactions, and adsorb the substance to be measured. There are reports of methods of immunoassaying using whole blood as a sample, not accompanied by hemolysis to avoid such problems (see Patent Documents 2, 3, 4, and 5).
When measuring components in blood cell such as intracellular proteins, blood cells must be lysed; therefore, the above-described methods which do not accompany hemolysis cannot be used. In such cases, methods which comprise separation of the blood cells of interest by flow cytometry followed by lysis of the isolated cells and measurement of the desired component in blood cell are used, but these methods require special equipments for flow cytometry and are troublesome.
On the other hand, as an example of convenient methods for measuring intracellular proteins, a method of immunoassaying MxA protein using as a sample for measurement, lysates of blood cells in whole blood prepared using a surfactant, has been reported (Non-patent Documents 1 and 2).    [Patent Document 1] Japanese Patent Application Kokai Publication No. (JP-A) H10-48214 (unexamined, published Japanese patent application)    [Patent Document 2] JP-A (Kokai) H06-265554    [Patent Document 3] WO 96/04558    [Patent Document 4] WO 02/73203    [Patent Document 5] JP-A (Kokai) 2004-45395    [Non-patent Document 1] Journal of Interferon Research, (USA), 1992, Vol. 12, No. 2, p. 67-74    [Non-patent Document 2] Pediatric Research, (USA), 1997, Vol. 41, No. 5, p. 647-650